From the published German Patent Application No. DE 2,107,437, a value device is known which comprises a body piece, liquid ducts opening themselves side by side at the smooth face of the body piece, as well as a resilient membrane which is pressed tightly against the face of the body piece around the openings of the ducts. The membrane is provided with a bulging facing the openings of the ducts. When the valve is to be closed, the bulging in the membrane is pressed simultaneously onto all of the openings. Thus, in this arrangement, a bulging must be prepared into the membrane in advance. It is a further drawback of the arrangement that the openings of the liquid ducts cannot be closed independently from each other.
From the published German Patent Application No. DE 2,752,549, a valve device is known in which several side ducts open themselves in a connecting channel of groove shape. The connecting channel can be closed between the openings of the side ducts by pressing a membrane by means of a pin against the walls of the connecting channel. This arrangement is not particularly suitable for apparatuses that require high precision, because a bulging of the edge of the membrane in the connecting channel may cause dosage errors.